Process of making protected metal



Sept. 1, 1925. 1,552,042

F. M. CRAPO PROCESS OF MAKING PROTECTED METAL Filed Oct. 21, 1924 A TTORNE Y.

' Patented Sept- I UNITED STATES PATENT OFFICE- FREDERICK II. CRAIPO, OF MUNCIE, INDIANA. I

PROCESS OF MAKING PROTECTED METAL.

Application filed October 21, 1924. Serial No. 744,976.

To an whom it may concern:

Be it known that. I, FREDERICK M. QRAro, a citizen of the United States, residing at Muncie, in the county of Delaware and State of Indiana, have invented a new and useful through a carbon-lined ingot mold for use in my invention; and Fig. 2 is a vertical sec tion through a bath of molten salts for treating the surface of an ingot in practicing my .invention.

In my Patent No. 1,501,887, granted July 15, 1924, I have described a zinc-coated article, specifically wire, and the method of producing it. This present invention embodies the generic invention set forth in the aforesaid patent, but relates to another specific way of producing such articles.

As explained in such prior patent, difliculty has been experienced in producing from which wire is drawn in the manufac-- suitably adherent zinc-coatings on wire and other articles of iron and low-carbon steel.

According to my present invention, I increase the carbon content of the iron or lowcarbon steel ingot before the ingot is worked to produce the final articles-or before completing the rolling of the ingot into the rod ture of wire. The surface increase incarbon content thus produced follows through the subsequent manufacturing operations, such as rolling and drawing, and remains as an increased carbon content in the surface with relation to that of the interior in the final product, such as wire. L

TlllS increase in carbon content in thesurface of the ingot may be obtainedin various ways. One simple way, shown in- Fig. 1, is to pour the molten iron or low-carbon steel 9. into ingot molds 10 which are lined with carbonizing material '11, such as carbon. As the iron cools, and solidifies, some of the carbon of the mold-lining is taken into the surface portion of the ingot, making such surface portion relatively richer in carbon than in the interior of the ingot. The ingot may be left in the ingot mold for a considerable time after solidification, if desired, to in crease the amount of carbon taken up.

Another way, shown in Fig. 2, is b treating the formed ingot 15, after solidi cation, to increase the carbon content of its surface. Such treatment may be by putting the ingot 15, while at a suitable carbon absorb ing temperature, with its surface in contact with a suitable carbonaceous materiaL. While such carbonaceops material may be of any suitable nature, one convenient form for it is in a molten mixture of salts containing cyanide; as illustrated in Fig. 2, where the ingot 15 (he-1d in jaws 14) is shown immersed in a bath 16 of such molten salts held in a container 17. The container may be'suitably heated externally, as by a'furnace 18.;

but the ingots may be'hot when immersed in the bath and may furnish at least a large part of the necessary heat. In this way a suitable permeative addition of the carbon into the surface of the iron'or lowecarbon steel ingot is obtained.

After the carbon content in the surface of the ingot has thus been increased, the ingot may be worked in any suitable manner, to produce the desired article. Then, after the article has been suitably cleaned and fluxed, it is zinc-coated in any suitable manner. The working of the ingot may consist, for instance, in rolling it-into rod, and drawing the rod into wire. After the article, such as wire, has reached its final form and size, it

and is desirably also annealed. This may method set-forth in my aforesaid prior patent, or'by some other method. The cleaned article, after being suitably fluxed, isthen zinc-coated in any usual or convenient way. This is perhaps most simply done by the method of hot galvanizing, consisting in dipping the article into a bath of molten zinc.. In the case of some articles, such as wire, such fluxing and dipping may both be obtained in a continuous process, by passing the wire or other article through a suitable flux, and then through the bath ofmolten zinc, in the well understood way.

The zinc coating thus produced is found to be quite closely adherent, and to resist peeling even when the wire or other article is subjected to deformation, such as bonding and twisting. p

I claim as my invention 1. The method of producing a zinc-coated in increasing the carbon content of the surface of an iron or low-carbon steel ingot with relation to.that of the interior of such ingot, working such ingot to produce the de sired article, and zinc-coating such article.

2. The method of producing zinc-coating iron or low-carbon steel wire, consisting in increasing thecarbon content of the surface of an iron or low-carbon steel ingot with re- 10 lation to that of the interior of such ingot,

rolling said ingot into rod, drawing such rod into Wire, and zinc-coating such wire.

3. The method of producing zinc-coated iron or low-carbon steel wire, consisting in forming an iron or low-carbon steel ingot, rolling said ingot into rod, drawing such rod into wire, and zinc-coating such wire; and increasing the carbon content in the surface of the iron or low-carbon steel with relation to that of its interior at a point in the process preceding the completion of the rolling operation.

In witness whereof, I have hereunto set' my hand at Indianapolis, Indiana, this 15th day of October, A. D. one thousand nine hundred and twenty four.

FREDERICK M. CRAPO. 

